Benishek was already considered vulnerable this cycle, and his 1st District was already counted among the three dozen most competitive races in the country. His narrow re-election victory in 2012 — 48.1-47.6 percent (a margin of 1,881 votes), made him an attractive target. But the seat leans Republican under most conditions.

The 73-year-old Wisconsin Republican's last eight months on Capitol Hill will likely be consumed with negotiations over legislation to reauthorize funding for the nation's highway and transit programs in his role as chairman of the subcommittee of jurisdiction.